Understanding General Requirements of the NEC, Part 9
Article 110 provides general requirements for all installations. Sec. 110.14 provides the general requirements for electrical connections. The first requirement is that any connectors (e.g., pressure terminal connectors) must be identified for the material of the conductor. You can’t mix and match the metals. The second requirement is that you install them properly. There’s some additional text, then the remaining requirements are organized as follows:
(A) Terminals. Gist: Make sure connections to these are mechanically secure without damaging the conductors.
(B) Splices. Gist: Any splicing devices shall be identified for the use.
(C) Temperature Limitations. Gist: The limiting value is the lowest rating of any connected termination, conductor, or device. A chain is only as strong as its weakest link.
(D) Terminal Connection Torque. Gist: Tighter isn’t necessarily better, use the correct torque value.
Common violations of Sec. 110.14 include crushing a connector instead of crimping it, using three conductors in a connector rated for only two, using copper lugs on aluminum conductors, using a higher temperature column in the ampacity table than the lowest rated connector or using a connector that is rated lower than the temperature column used to determine ampacity, and overtightening of connections. Perhaps the least recognized of 110.14 violations is the overtightening of connections.
When you tighten to the correct torque value, you obtain maximum clamping power; going past that point dramatically decreases clamping power. If you have a Bellville washer, you tighten it until it’s just hitting flat. If you have a split ring lock washer, you tighten the connection just enough to close the ring (like the Belleville washer, it will be just hitting flat). A split ring washer compressed this way will exert maximum pressure against the threads, locking them into place. If you crush the spring out of the washer, it is then essentially a flat washer and no longer contributes to making the connection mechanically secure.
About the Author
Mark Lamendola
Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.
Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.
Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.